There have been three human cases of West Nile Virus in California this year, with one fatal case, according to the California Department of Public Health.

The Allegheny County Health Department on Monday confirmed that additional mosquito samples have tested positive for West Nile Virus. The health department will treat areas for mosquitoes in the communities of Hazelwood,

The disease causes serious illnesses in about 1 in 150 infected people, and can prove fatal. No human cases have been reported in Pennsylvania or New Jersey this year.